Concentrating photovoltaics Technology (CPV) has become a relevant technology for solar energy conversion. Especially under high concentration, the use of cost-effective, high-efficiency multi-junction solar cells enable high system efficiencies and a competitive levelized cost of electricity in regions with a large fraction of direct irradiance. However, the development of this technology requires the utilization of specific indoor/outdoor characterization techniques that are not yet widely known. A review of current hot topics in indoor/outdoor CPV characterization in energy and performance testing will be presented and discussed during this short SOPHIA on line course.

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A Concentrator photovoltaics (CPV) system converts sunlight directly into electrical energy by concentrating the sunlight received by an optical system onto a very-high efficiency solar cell in a smaller area. This can dramatically reduce the amount of semiconductor needed and, at the same time, the use of concentration increases the electrical efficiency of the solar cell. Both factors allow a competitive levelized cost of electricity in regions with a large fraction of direct irradiance. Conversely CPV modules are made up by lenses or mirrors that concentrate light on smaller PV receivers, which have to be installed on performing high-accuracy sun trackers. The cell-optics assembly is completed by heat sink and housing elements that constitute a complex mechanical, optical and electrical element that requires specific characterization techniques in order to assess its performance in a meaningful and reproducible way.

During this short course, hot topics in CPV characterization will be presented and discussed by highlighting requirements, procedures and instrumentation issues specific to CPV systems. Current version of the IEC 62670 series on the performance rating of concentrators will be presented, whose methods are under test in the SOPHIA Round Robin of CPV modules. Finally, spectral parameters and indoors tests relevant to the analysis of multi-junction cell-based CPV devices will be presented.

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Introduction to CPV technology and its characterization

Concentrating Photovoltaic technology CPV has become a relevant technology for solar energy conversion in electricity enabling high system efficiencies of PV system comparable to more conventional solar thermal and with competitive levelized cost of electricity in regions with a large fraction of direct irradiance. Conversely CPV modules are made up by complex mechanical, optical and electrical components which have to be installed on performing high-accuracy sun trackers to concentrate light on smaller PV receivers. That requires specific characterization techniques in order to assess its performance in a meaningful and reproducible way- This introduction provides an overview of the main scientific/technical aspect related to CPV characterization by leaving to next speeches the opportunity to deepen on them

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Power Rating of CPV Modules

The International Electrotechnical Commission’s Technical Committee 82 Working Group 7 (IEC TC82 WG7) is devoted to the development of international standards for Concentrator Photovoltaics (CPV). These include the IEC 62670 series related to the rating of CPV. IEC 62670-1 (Concentrator Photovoltaic (CPV) Performance Testing – Part 1: Standard Conditions) has been published in 2013 and defines the standard conditions for the rating of CPV devices. IEC 62670-2 (Concentrator Photovoltaic (CPV) Performance testing – Part 2: Energy Rating by measurement) is in the draft phase and will define methods for the performance of a long term energy output measurement of CPV systems.Last but not least IEC 62670-3 (Concentrator Photovoltaic (CPV) Performance Testing – Part 3: Performance Measurements and Power Rating) will define procedures for a power rating of CPV modules and systems

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Sophia CPV Module Round Robin: Power Rating at CSOC

In the frame of the European project SOPHIA a concentrator photovoltaic (CPV) module measurement round robin has been initiated. The round robin includes measurements of four CPV modules at seven different test laboratories located in Europe.IV curves of the modules are measured with different measurement equipment under various climatic conditions.The aim of this activity is to perform at each site a rating of the modulesat concentrator standard operating conditions CSOC according to IEC 62670-1. The outcome of the round robin is intended for direct feedback to the current draft standard IEC 62670-3 “Concentrator Photovoltaic (CPV) Performance Testing - Performance Measurements and Power Rating”. Data treatment and the chracteristics and accuracy of different power rating methods are discussed.

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Spectral characterization of DNI, application to CPV. Results of the Sophia spectral network

nAbstract: A methodology to determine the spectral influece based on component cells (placed in collimating tubes to form a spectroheliometer) is presented, useful to characterize spectrally Multi-Junction (MJ) solar cells and Concentrating Photovoltaics (CPV) modules and systems. The Spectral Matching Ratio (SMR) between two subcells for a given spectrum is defined and then can be used to filter those moments whose spectra are equivalent to the reference one (AM1.5D-G173-03).Furthermore, annual data from a spectroheliometer can be used to determine the periodic spectral influence in a given location. In the frame of the European project SOPHIA, a spectral network based on component or isotype cells has been created. Among the members of this project, several instruments were installed in the last years, allowing the collection of minute-resolution spectral data useful for CPV technology across Europe.

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Instruments and methods for indoor characterization of CPV devices

Indoor characterization tools are valuable for the development and optimization of concentrator PV systems, and critical for the large-scale deployment of CPV. Yet they remain not widely known or understood. In this talk we will review the main instruments and methods currently used in indoor testing of CPV optics and modules. Notably, we will describe the principles of a CPV solar simulator and the main requirements it should fulfill in order to provide significant measurements. Furthermore, we discuss appropriate reference sensors for light intensity and spectrum, typically based on component cells and single-lens concentrator units (mono-modules). Methods for meaningfully assessing irradiance and spectral conditions are detailed.